Process for the fixation of nitrogen



, ?atented a. 25, 1938 2,134,206

UNITED STATES PATENT OFFICE PROCESS FOR THE FIXATION 0F NITROGEN Ovid E. Roberts, Jr., Washington, D. C.

No Drawing. Application May 1,1835,

Serial No. 19,328 v 8 Claims. (01. 2o4-31i My invention relates to a process for the flxalarger quantity of ozone. The relative proportionv tion of nitrogen. Although it is known that of these substances so formed changes rapidly, nitrogen and oxygen may be combined through until practically no oxide of nitrogen is produced. the use of the electric are as a source of energy, This I have found to be due to the fact that the 5 the relation of the output of oxide of nitrogen, ozone so formed filters or screens out the rays es- 5- so formed, to the current consumed, is such that sential to the ionization of the nitrogen. There the process is, under most commercial conditions, may be other contributing factors, but I deem uneconomic. this of greatest influence.

I have discovered that the economic produc- To produce the conditions optimum to the tion of an oxide of nitrogen by a direct combinaformation of the oxide of nitrogen, I find that it 10 tion of the nitrogen and oxygen molecules deis desirable that the oxygen content of the gas pends, not upon one, but upon a number of facmixture should be well below that of the oxygentors, and, equally, upon the relation of each of nitrogen air ratio. An oxygen content of less these factors to one another. The major facthan 7.5 per cent is desirable. The exact upper tors are: temperature energizing influence; perlimit of the percentage of oxygen in the gas mixcentage of oxide of nitrogen present; percentage ture will vary with the rate at which the ozone of ozone present; percentage of oxygen present; is formed and at which it is removed. Because percentage of nitrogen present; location of of its filtering action hereinbefore described, the

source of, and the character of, the energizing limitation of the formation and/or accumulationinfluence; and the screening and/or flltering of appreciable amounts of ozone in the energizagencies present. ing zone is essential to successful formation of Under the conditions imposed by the electric the oxide of nitrogen. arc, but a very small part of the current expend- In the operation of my process, I pass a mixed can be said to be efficiently. directed toward ture of oxygen and nitrogen, preferably under a the combination of oxygen and nitrogen. Most super-atmospheric pressure, through a zone in 215i of this current is directed toward the generation which they are subjected to the influence of a of high temperatures which are, if not actually high frequency brush discharge, or other source inhibitive to the formation of the oxide, at least of energizing rays, preferably in the presence of a conducive to its rapid dissociation. The elimgaseous element adapted to screen out the ray ination of the high temperature factor is essenor rays contributing to the ozonation of the tial to any successful economic process: and the oxygen. For this purpose the preferred element elimination or subjection of forcesof distribution is hydrogen. The gas mixture may be such as is also necessary. might be produced in the course of oxygen ex- I have found that it is possible to substitute traction by the Linde or similar processes, or it a high frequency brush discharge for the electric may be otherwise produced. The oxygen in this are to constitute What I have termed a Source Of instance is less than 7.5 per cent of the mixture. n zin fi m I am fully c niz of the The gas mixture is kept in motion as by flowing, met that such a source of energy might be condensation, and/or liquefaction. The gas mixduced by other means, such as certain cathode ture ma thenhe cled' or 'm the event that 40 rays, and preferably those emitted by electrodes it has 3 sumciently liigh content be 40 of aluminum and/or chromium, and therefore f i do not limit myself to the high frequency brush 5 1; i i gggzi a g g' g it may be e discharge as the sole source of this required en- It Wm be apparent that various means may be ergy. Such a high frequency brush discharge h h e f rm u f Oz m may be produced by means comparable to those utilized to c eck t e excessw 0 a on 0 o 4 employed in the production of ozone and thereby accelerate the ionization of the hi: This energizing force appears to be a my or trogen essentlalto the formation of the oxide OL- ray group having a wave length in the neighbornitrogen Dunno of the oxygen'mtmgen hood of 1700 to 2100 angstroms, and not exceedture by the high nitrogen content gas resulting mg 2250 from the reaction is a method available under 50,

1 have found t t when a mixture 0f xygen most operating conditions. I may also react such and nitrogen in atmospheric proportions is subozone with an agent Such 85 Oil Ot yp of jected to the ionizing influence of a high fresubstance that may be readily oxidized. Such quency brush discharge, there is formed .a small oils asthe linseed oil type, asphalt type. and cerquantity of nitrogen tetroxide or peroxide ands. tainnatunal hydrocarbons, e. g., methane, ethane, "ii" to the oxygen content of the gas mixture under treatment and will be less required where the oxygen content of the mixture is low.

I fully recognize the fact that variations of the pressure under which the reaction may be conducted will directly influence the rate of reaction. As a generalization, I find that the lower the oxygen content of the gas mixture, the higher the pressures under which the reaction may be employed to advantage. I do not desire to limit my claims, therefore, to any set of pressure conditions.

It is essential, if the reaction is to proceed properly, that the oxide of nitrogen be removed as rapidly as practicable. I find that this may be best accomplished by condensation, and prefer this method to absorption, the formation of nitric or nitrous acid, or the reaction with a metallic salt, although such method is feasible. The pro-' cesiure adopted may vary with the requirements of operating conditions, and, recognizing this, I do not restrict myself to any specific procedure in this instance.

I have mentioned the influence of certain filtering or screening agents in the reaction zone, and have cited the influence of ozone in filtering out the rays which energize nitrogen in formation of the oxide of nitrogen. I have found that the presence of certain gases, of which hydrogen, methane and carbon monoxide are examples, appears to have the effect of reducing the amount of ozone and increasing the formation of the oxide of nitrogen.

Whether this is an example of ray filtration or is an instance where the ozone is removed by reaction with such agents, I do not know. Some evidence would lead to the conclusion that a dual function is served. Whatever the precise explanation is, the employment of such an aid may be of real value under certain operating conditions.

I have found that molecules of certain substances appear to possess a. specific property which is as much an individual characteristic of that substance as its specific gravity melting point, boiling point, refractive index, etc. This property is one by which the molecule utilizes the energy of a specific ray with the resultant effect of a high degree of excitation. This effect assumes the nature of something akin to energy transformation or accumulation. There appears, for a period, a storage of energy received with a "spill-over" or other evidence of cumulative effect. The molecule appears to be activated by a specific light ray or ray groups, molecules of other substances reacting in a like manner toward other light rays or ray groups.

The resultant effect of such excitation or energization is to induce a state conducive to combination with other molecules or to polymerization. This appears a general property shared by molecules of many substances.

It is known that each chemical element may, under suitable conditions, be caused to emit certain specific light rays characteristic of such elements. Certain rays may be found in the spectrum of more than one element but their proportion. general grouping, and arrangement are a characteristic of the element producing them. The two K-lines, for example, characterizing the spectrum of calcium, may be found war-in the adjacent chemical elements titanium, va-

to use a cored arc.

nadium, and chromium, in the natural series of the elements.

It might be inferred that the simple expediency of resorting to a prism or other device for the production of a monochromatic light ray of definite frequency would suffice for the purpose indicated. I have not found this to be the case. While it might work for certain types of reactions, it is at least inferior to other types which I have encountered.

In utilizing specific rays or ray groups for energizing a desired reaction, I prefer to reenforce certain well known emissions and by the superimposition of the desired frequency upon the characteristic spectrum, gain the effect desired, rather than by limitation of the energizing source to emission of simply the frequency desired.

Where the spark or brush discharge method is used, the energizing rays employed are those emitted in the brush type of discharge. To gain the effect of a specific ray or my group required, I may adopt one of several methods. I may selost for my terminals a metal whose spectrum is characterized by a ray or my group essential for its energizing value. For this reaction I desire light ray for energizing purposes of from 1700 t 2250 angstroms.

I have found terminals of aluminum, chromium or nickel suitable for the purpose. It is within the scope of my invention to employ one terminal of aluminum and another of a different metal. Where, as in-a brush discharge, there may be a multiplicity of discharge points, I may have anodes of any number of different metals as, for example, the three indicated.

I find it possible to produce the energizing rays by means of anodes kept moistened by salt solution of the chemical elements producing rays of the desired character. If I employ this method, I may use a single metallic salt or several salts in a sufficiently moist state to keep the anode damp. For this type of terminal I prefer to use the oxide or sulphate of the metal, the spectrum of which is desired.

It is within the scope of my invention to use a modified electric are as a source of energy. such modification being made by one of three methods. In one, I use nickel or chromium as an anode. In another method I use an anode seat made of oxide or oxides of chromium, aluminum and/or nickel.

It is also within the province of my invention Such a practice is distinct from that employed in producing the well known flaming arc in that its object may have no concern with the rays comprising that portion of the spectrum to which we are optically sensi-' The core of such an arc may be composed ofan oxide of the desired metal or the metal itself. It may also be a mixture of the metal and oxide thereof. The core may be moulded and fixed in a carbon as required, sumcient clearance being provided for such feeding in the formation of said carbon and core materials.

One procedure that may be followed is to use approximately 4 per cent oxygen in the oxygennitrogen mixture at slightly above atmospheric pressure in the presence of cloths or surfaces continuously saturated with linseed oil and dis-'- tributed or suspended in the reaction chamber. The oxidized oil should be removed continuall andreplaced by new iinseed oil.

Having thus described my invention, I claim 1. A process of nitrogen fixation including the step of subjecting a mixture of nitrogen and oxygen wherein the oxygen content of the mixture is less than 7 /z% to a high frequency brush discharge.

2. A process of nitrogen fixation including the' steps of subjecting a mixture of nitrogen and oxygen, wherein the oxygen content is well below the oxygen-nitrogen air ratio, to a high frequency brush discharge and limiting the formation and accumulation of appreciable amounts of ozone in the energizing zone.

3. The process set forth in claim 2 carried out under superatmospheric pressure.

4. The process set forth in claim 2 carried out in the presence of a gaseous agent of the group consisting of hydrogen, methane and carbon monoxide.

5. The process set forth in claim 2 carried out in the presence of an ozone oxidizing hydrocarbon.

6. The process of nitrogen fixation comprising the steps of subjecting a mixture of nitrogen and oxygen, wherein the oxygen content is less than l /2% of the mixture, to a high frequency brush discharge to produce oxides of nitrogen, separating said oxides and recirculating the low oxygen content mixture.

7. A process of nitrogen fixation which comprises, introducing a potentially reactive mixture of oxygen and nitrogen into a reaction zone,

definitely limiting the oxygen of the mixture to less than substantially 7 per cent, and cited.- ing a reaction between the components of the mixture by irradiating the mixture in said zone with electromagnetic energy, such energy comprising essentially a ray group of from 1750 to 2250 angstroms.

8. A process of nitrogen fixation which comprises, introducing a potentially reactive mixture of oxygen and nitrogen, into a reaction zone,; definitely limiting the oxygen content or the mixture to less than 7% per cent, and effecting a reaction between the components of the mixture by irradiating the mixture in said zone with electromagnetic energy comprising essentially a ray group of from 1750 to 2250 angstroms and limiting the formation and accumulation of appreciable amounts of ozone in the reaction zone.

v OVID E. ROBERTS, JR. 

